There have been already suggested many valves wherein, by operating an operating lever, a movable valve body is moved relatively in sliding contact with a fixed valve body contained in a main valve body to connect or disconnect a passage of a fluid or, in other words, to control the valve to be opened, closed, switched, adjusted or used to mix fluids.
Now, for this kind of valve, there are such various requirements as in the following:
(1) Even though the movable valve body is always in sliding contact with the fixed valve body, the movable valve body should be lightly operated by the operating lever.
(2) The operation by the operating lever should be able to be maintained to be light for a long period.
(3) The maintenance service of each valve body should be simple and, if possible, should not be required at all.
(4) As a matter of course, the sealing between the respective valve bodies should not vary and the fluid should not leak out even in a long use.
(5) The respective valve bodies should be simple to make.
In such various already suggested valves for fluids as, for example, valves for mixing hot water and cold water with each other, in consideration of the wear resistance between the respective valve bodies, the respective valve bodies have been often formed of such comparatively hard material as a metal or sintered aluminum oxide so as to be compact. However, if so formed, the respective valve bodies will improve in the wear resistance but will not smoothly slide between them and, as shown in FIG. 4, the sliding torque applied to the operating lever of the valve for mixing hot water and cold water will be considerably large in the initial period.
Therefore, in order to smooth such sliding, the respective valve bodies are painted with a lubricant on the surfaces.
However, the lubricant applied to paint the surface is so likely to flow out that, in the case of a long use, it will be difficult to maintain the initial operation characteristic.
Thus, ceramics themselves have a high hardness and are high in the wear resistance but are generally poor in the self-lubricatability. Ceramics have not yet been suggested as materials solving it and applicable to valves.
The present invention is made in view of such fact as in the above and its object is to provide a valve wherein, even in the case of a long use, the fluid can be always lightly and stably connected or disconnected by the operating lever.